It is well known that silver halide photographic materials are developed and intensified to amplify image-formation. It is described, for example, in Friedman, "History of Color Photography", 2nd Ed., page 406 (1956) that in the presence of a coupler, a paraphenylenediamine color developing agent is oxidized by the decomposition of hydrogen peroxide on the surface of a catalyst followed by coupling it with the coupler to form a dye. Further, various photographic methods utilizing the decomposition of peroxide compounds on the surface of noble metals are described in U.S. Pat. Nos. 674,490, 3,684,511, 3,761,265, 3,765,890, 3,776,730, and 3,817,751 and British Pat. Nos. 1,329,444 and 1,341,719. On the other hand, a color intensifying method employing a cobalt complex on the surface of noble metals is described, for example, in Japanese Patent Application (OPI) Nos. 9728/73, 9729/73, 48130/73, 84229/74, 84240/74, 97614/74, 102340/74 and 102314/74.
Color intensifying methods employing halogenous acids such as chlorous acid are described in Japanese Patent Application (OPI) Nos. 53826/76 and 13336/77. A color intensifying method employing an iodoso compound such as iodoso benzoate is described in Japanese Patent Application (OPI) No. 73731/77.
These compounds which have an intensifying effect such as peroxides, halogenous acids, iodoso compounds and cobalt complex compounds (III) are called intensifying agents and the processing bath which includes the intensifying agent are called an intensifying bath.
Color image intensifying methods which utilize the catalytic action of peroxide compounds or cobalt (III) complex are generally well known. Particularly, the intensification of hydrogen peroxide appears to be most efficient with respect to the amplifying effect. These methods are known as methods of intensifying images which comprises imagewise exposing silver halide photographic materials, forming developed silver nuclei from thus obtained latent image with development, redox-reacting an intensifying agent with a color developing agent on the developed silver nuclei which acts as a catalyst to form an oxidation product of the developing agent, which reacts with a color-forming coupler to produce a colored image with high density. In other words, the intensifying method means that according to the methods that color photographic materials are color developed and then dipped in a intensifying bath, or are developed with black-and-white developing solution, dipped in a color developing solution and finally dipped in an intensifying bath, developed silver nuclei are formed from a latent image by development and a color developing agent is retained in a layer of photographic materials, and thus image is intensified by the redox reaction of the color developing agent retained in photographic materials with the intensifying agent in an intensifying bath on the developed silver nuclei. Therefore, in order to intensify an image with high efficiency, a large amount of developing agent must be retained in a layer of photographic materials to be carried in the intensifying bath. Furthermore, the developing agent must be quickly oxidized with the intensifying agent for a short time on the silver nuclei as a catalyst before the developing agent in a layer is diffused into the intensifying bath.
A specific example employing a developing agent having a hydrophobic property, which is incorporated in a developing solution, is described in U.S. Pat. No. 3,816,134 and Japanese Patent Application (OPI) No. 30333/78. Furthermore, Japanese Patent Application (OPI) Nos. 13335/77 and 19829/78 disclose that fog caused by the intensifier is inhibited without degrading the activity of the catalytic nuclei. Thus, mixing the component of the developing solution into the intensifier is a serious problem of the image intensifying method.
It is inevitable that mixing the intensifying inhibitor into the intensifier lowers the intensifying activity and that the efficiency of the intensifier is changed by the mixture with the developing agent. On the other hand, the intensifying developing process is not desirable because the processing steps can not be simplified due to the use of the intensifying step which is not used in a conventional method one or more processing steps being increased. The simplification of steps is disclosed in U.S. Pat. Nos. 3,847,619 and 3,923,511. These patents disclose that development, intensification and bleach may be carried out in a mono-bath employing a cobalt (III) complex. However, it is difficult to obtain excellent color images in case where the photographic material with a low silver content is developed in a mono-bath type intensifying developing solution employing cobalt (III) complex because of fog caused by the intensification and low image density. These technics are extremely important and useful in making economical use of silver resources, because developed silver is used as a catalyst and high image density is obtained with a small amount of silver.
However, the image intensifying method using hydrogen peroxide which has excellent amplifying efficiency has not yet been put into practice. It has not been practically utilized because of problems such as: (1) an increased number of processing baths are needed as described above and accordingly, the processes are not simplified compared with the conventional method; (2) color mixing and fog occur in the photographic materials; and (3) the intensifying activity decreases with the passage of time. This is caused by the presence of components of the developing solution (for example, halogen ion color developing agent, etc.) are included in the intensifying solution by photographic materials. It should also be noted that reproducibility of the images by intensifying solution is very difficult, because intensifying solution is very unstable with the passage of time.
German Pat. No. 1,813,920, and Japanese Patent Application (OPI) Nos. 13335/77 and 127555/80 disclose that development and intensification are carried out in a mono-bath at the same time using hydrogen peroxide. However, although hydrogen peroxide is added in a conventional color developing solution, a mono-bath intensifying developing effect can hardly be obtained in photographic materials having a low silver content because potassium bromide (usually potassium bromide is added in an amount of several hundreds mg/l) is present in the color developing solution as described hereinbefore. Further, when a nitrogen-containing heterocyclic compound type organic anti-foggant is not present in a mono-bath developing intensifying solution a great deal of fog is created. However, the effects of a mono-bath intensifying solution as obtained in this invention can not be obtained by only mixing a conventional color developing agent with hydrogen peroxide.